Are You Overlooking This Hidden Source of Joint Pain, Gut Woes and Thyroid Problems?

By Tucson Functional Medicine on October 31, 2022 0 Comments

Dr. Joe Mercola

  • Plant lectins act as a built-in defense mechanism that ensures survival by triggering an adverse reaction in predators; in humans, they attach to your cell membranes, often wreaking havoc on your health.

Many lectins can cause inflammation, damage your nerves and kill your cells, while some increase your blood viscosity, interfere with gene expression, and disrupt your endocrine function.

While it is nearly impossible to avoid all lectins due to their presence in countless foods, if you are struggling with an autoimmune disease or another chronic health issue, you may benefit from a lectin-restricted diet.

Among the most problematic lectin-containing foods are beans, grains, legumes, and members of the nightshade family like eggplants, potatoes, and peppers

High-lectin foods can be made safe to eat through proper soaking and cooking, as well as fermenting and sprouting; using a pressure cooker is particularly beneficial for beans.


Lectins can be a common and hidden source of health problems and weight gain, even if you eat an otherwise healthy diet. Lectins have been linked to autoimmune reactions and inflammation, and many are toxic to your cells and nerves. In addition, specific lectins may increase your blood viscosity, interfere with gene expression and disrupt your endocrine function.

If you are dealing with an autoimmune disease, you will need to be especially careful with lectins, and you may benefit from a lectin-restricted diet. That said, it is nearly impossible to avoid lectins 100 percent of the time. I do not recommend a lectin-free diet simply because you’d miss out on antioxidants and other nutrients in lectin-containing foods, including many otherwise nutritious vegetables. A better approach is to consume lectins occasionally and pay attention to how they affect you.

Your body may react to the lectins if you consistently experience bloating, gas, and joint pain after eating beans. How you prepare lectin-containing foods makes a big difference in your body’s ability to handle them and using a pressure cooker is by far the best approach. If you’ve been eating a whole-food diet yet are struggling with unexplained weight gain and/or stubborn health problems, it might be time to limit the lectins.

What Are Lectins?

Lectins are sugar-binding plant proteins that attach to your cell membranes. They are a form of protein found in all kinds of plants and animal foods, which some consider being a low-level toxin. Instead, lectins provide a built-in defense mechanism that triggers an adverse reaction in predators, aiding their survival. About plant lectins, Dave Asprey, founder of Bulletproof.com, states:

“There are countless varieties of lectins in nature … Plants evolved to reproduce. They are not interested in being a food source for you or insects or fungi. Since they are not good at running away, plants developed natural pesticides and repellents to protect themselves and their seeds from hungry animals.”

Precision Nutrition shares some additional information regarding lectins:

“Lectins are abundant in raw legumes and grains and most commonly found in the part of the seed that becomes the leaves when the plant sprouts, also known as the cotyledon, but also on the seed coat. They’re also found in dairy products and certain vegetables.

Lectins in plants are a defense against microorganisms, pests, and insects. They may also have evolved as a way for seeds to remain intact as they passed through animals’ digestive systems for later dispersal. Lectins are resistant to human digestion, and they enter the blood unchanged.”

Healthline states, “The ‘stickiness’ of lectins makes them prone to attaching to your intestinal wall. This is the main reason why excessive lectin intake causes digestive distress.” High levels of lectins are found in beans, grains, legumes, dairy, and vegetables within the nightshade family. However, many other foods contain lectins at lower and less potentially toxic amounts.

How Lectins Can Harm Your Health

Because they resist digestion, lectins act as “antinutrients,” which means they have a detrimental effect on your gut microbiome by shifting the balance of your bacterial flora. One of the worst culprits is wheat germ agglutinin (WGA), which is found in wheat and other seeds in the grass family. I consider Dr. Steven Gundry, author of the book “The Plant Paradox: The Hidden Dangers in ‘Healthy’ Foods That Cause Disease and Weight Gain,” to be one of the best sources of information regarding lectins can harm your health.

He suggests some plant lectins can contribute to a leaky gut by binding to receptor sites on your intestinal mucosal cells, thereby interfering with the absorption of nutrients across your intestinal wall. Compared to WGA, gluten is a minor problem, says Gundry. That’s because WGA is one of the most efficient ways to induce heart disease in experimental animals. Due to their adverse autoimmune and inflammatory effects, lectins are particularly toxic to anyone with an autoimmune disorder.

If this is you, you may want to consider eliminating lectins or drastically reducing your intake. One manner in which lectins stir up trouble in your body is through molecular mimicry. For example, by mimicking proteins in your thyroid or joint spaces, lectins can trick your body into attacking your thyroid gland and contributing to rheumatoid arthritis. Part of this disease process results in lectins and lipopolysaccharides (also known as endotoxins) penetrating your gut wall, causing a robust immune response.

Should You Avoid Beans and Other Lectin-Rich Foods?

Suppose you are struggling with an inflammatory or autoimmune condition. In that case, you may be among those who need to be careful concerning lectin-containing foods — specifically beans and legumes, grains, and nightshade vegetables. Gundry said, “My research and others suggest that lectins cause most heart disease, arthritis, dementia, diabetes, and all autoimmune disease.” A lectin-restricted diet may be helpful if you are dealing with:



Are All Lectins Bad for You?

While Gundry declares lectins the greatest danger in the American diet, especially for those with an autoimmune disease, in small amounts, the truth is that some lectins can provide valuable health benefits. Precision Nutrition states: “Lectins are thought to play a role in immune function, cell growth, cell death, and body fat regulation.” But unfortunately, it seems most problems arise from overconsumption or continued consumption, even in small amounts, of specific lectins your body cannot tolerate.

I think it would be a mistake to assume all lectins are harmful to you. For example, one of my favorite foods, avocados, contains lectin agglutinin (Persea Americana agglutinin), but I continue to eat them regularly and would not consider them a food to avoid. Avocados are a healthy food, and research indicates the agglutinin found in them is devoid of specificity for carbohydrates — it interacts with proteins and polyamino acids instead.

Although tomatoes, as part of the nightshade family, are often listed among the most problematic lectin-containing foods, the heat of cooking them brings about some positive benefits. The antioxidant lycopene in tomatoes has enhanced bioavailability from heating, making tomatoes healthy in other ways. Bean lectins, however, are accompanied by more potentially toxic or allergenic effects. Beyond their lectin content, beans also are high in net carbs.

For this reason, they are best avoided in the initial transitional stages of a ketogenic diet. As you can see, the choice for or against lectins hinges on the particular food in question and the effects lectins have on the eater. While a good deal of controversy has been stirred, the presence of lectins is by no means a sole determinant of the overall value of a particular food to your diet.

The Most Damaging Lectins to Avoid

Grains and legumes such as black beans, kidney beans, lentils, lima beans, and soybeans contain the highest lectins. Other potentially damaging lectin-containing foods are:

Dairy products, especially those originating from grain-fed animals

Legumes — all beans, peanuts, and soy

Nightshade vegetables, including eggplant, potatoes, and peppers

Wheat and other seeds of the grass family, such as barley, buckwheat, corn, millet, oats, and rye

Most lectins are proinflammatory, triggering inflammation and creating advanced glycation end products. C-reactive protein is one example of the many lectins you have circulating in your body right now, and it’s used as a marker of inflammation. However, lectins are also immunotoxic (capable of stimulating a hyperimmune response), neurotoxic and cytotoxic, meaning they’re toxic to your nerves and cells and may induce apoptosis (cell death).

Specific lectins can increase your blood viscosity by binding to your red blood cells. This makes your blood cells sticky, resulting in abnormal clotting. In addition, some lectins, such as WGA, have been known to interfere with gene expression and disrupt your endocrine function.

Equally problematic is the reality lectins promote leptin resistance, thereby increasing your risk of obesity. All of these factors can predispose you to disease. Therefore, if you have any health problem to which lectins are a suspected contributor, you’d be wise to eliminate the following foods from your diet entirely:

Cashews, peanuts, and unfermented soybean products. When it comes to soy, your best choices are fermented varieties such as miso, natto, tamari, and tempeh.


Corn-fed meats. This includes most meats sold in grocery stores. You can avoid factory-farmed, corn-fed meat by ensuring the meat you buy is certified grass fed by the American Grassfed Association.

Milk with casein A1. Casein A2 is the standard protein in milk, present in milk from buffalo, goats, sheep, and some Jersey cows. Unfortunately, most cows today are casein A1 producers, and most store-bought milk is A1, even if it’s organic. This is because A1 proteins are metabolized in your gut to make beta-casomorphin, which can attach to beta cells in your pancreas and incite an autoimmune attack.

You may have mistakenly believed you’re lactose intolerant when the effects could be a response to the casein A1 in certain types of milk. The best milk to drink is raw milk from organic, grass-fed, casein A2-producing cows. Jersey cows produce casein A1 or A2, so you’ll need to check with the farmer to confirm the type of milk made. Avoid milk from Holsteins because they have casein A1.

Ways to Cut the Lectin Content in High-Lectin Foods

After eliminating the worst offending high-lectin foods from your diet, you can further reduce lectins in your diet with the following tips:

Peel and deseed your fruits and vegetables. The skin (or hull) and seeds contain the highest lectins. For example, you’ll want to remove the seeds from peppers and tomatoes before eating them.

Choose white grains over brown. Gundry believes white rice is preferable to brown because “those who eat rice as their staple grain have always stripped the hull off brown rice before they eat it. That’s because the hull contains all the dangerous lectins.” If you want to avoid lectins, the best way to eat bread safely is by choosing organic grains and then using yeast or sourdough, which effectively breaks down the gluten and other harmful lectins.

Sprout beans, grains, and seeds. Sprouting deactivates lectins, although there are exceptions. For example, do not sprout legumes, but the lectin content is enhanced when growing alfalfa.

Eat fermented foods. Fermentation effectively reduces harmful lectins, and all sorts of vegetables can be fermented, boosting their health benefits.

Use a pressure cooker. The best way to neutralize lectins when cooking is by using a pressure cooker. Gundry says, “If you’re cooking with beans, tomatoes, potatoes, and quinoa, the pressure cooker is your best bet … But, … it won’t even touch the lectins in wheat, oats, rye, barley, or spelt.” Avoid slow cookers since the low cooking temperatures are insufficient to remove some lectins.

Tips for Reducing Lectins in Beans and Potatoes

If you choose to eat beans, it’s imperative you prepare and cook them properly, mainly because eating raw or undercooked beans can have acute, toxic effects. For example, the toxin phytohemagglutinin is common in wide varieties of beans, and concentrations are exceptionally high in natural red kidney beans.

The U.S. Food and Drug Administration (FDA) states eating as few as four or five raw beans may cause phytohemagglutinin toxicity, often marked by extreme nausea, vomiting, and diarrhea. In addition, the FDA notes several incidents of poisoning concerning the undercooking of beans using slow cookers and Crockpots. Therefore, to make beans safer to eat, be sure to:

Soak the beans in water for at least 12 hours before cooking, changing the water frequently. Adding baking soda to the soaking water will further neutralize the lectins.

Discard the soaking water and rinse the beans.

Cook for at least 15 minutes on high heat or use a pressure cooker. Many people swear by the InstaPot.

The lectin content in potatoes, a member of the nightshade family, will also be reduced by cooking, although only 50 to 60 percent. On the positive side, most potatoes contain digestive-resistant starch, which consists of complex starch molecules that resist digestion in your small intestine. Instead, these starches slowly ferment in your large intestine, acting as prebiotics that feeds your healthy gut bacteria.

Why You Should Limit, Not Eliminate, Lectins

Some researchers, like Anthony Samsel, believe the lectin damage is related to glyphosate contamination. Gundry and others make a strong case against lectins due to their potential to wreak havoc on your health. However, given the number of lectin-containing foods, eliminating them from your diet would be nearly impossible. The list of lectins within the vegetable kingdom alone is lengthy, and some lectins do have health benefits.

Many lectin-containing vegetables also contain polyphenols, which are micronutrients with antioxidant activity that play an essential role in preventing and reducing cancer, diabetes, heart disease, and neurodegenerative conditions. Polyphenols are also regarded as prebiotics, increasing the ratio of beneficial bacteria in your gut, which is essential for disease prevention and weight management.

While you don’t want to miss out on the polyphenols, it’s well worth your time to experiment and identify lectins that may be problematic for your body. If you eat a healthy, whole-food diet but continue to have health problems, it may be time to limit the lectins. Such a change might be the key to improved health and healing.

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